Method of making a flat wire grid



Dec. 12, 1967 R. R. CAHEN ET AL 3,357,459

METHOD OF MAKING A FLAT WIRE GRID Filed June 18, 1965 3 Sheets-Sheet l Fig: 2

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Dec. 12, 1967 R. R. CAHEN ET AL 3,357,459

METHOD OF MAKING A FLAT WIRE GRID Filed June 18, 1965 5 Sheets-Sheet 2 Fi9-4A AYWW Dec. 12, 1967 R R CAHEN ET AL METHOD OF MAKING A FLAT WIRE GRID Filed June 18, 1965 3 SheetsSheet 5 lIIIIIl/l/(l/III/IA United States Patent O 3,357,459 METHOD OF MAKING A FLAT WIRE GRID Roger Raymond Cahen and Jean Pierre Driffort, Levallois, Hauts-d'e-Seine, France, assignors to CFT-Compagnie Francaise de Television, a corporation of France Filed June 18, 1965, Ser. No. 464,971 Claims priority, application France, June 25, 1964, 979,564 3 Claims. (Cl. 140-71.5)

ABSTRACT OF THE DISCLOSURE A method of making a wire grid for a cathode ray tube in which a continuous wire is wound on two spacedly parallel, grooved winding rods to form two parallel sheets of parallel wires, the two sheets are brought to rest on a second pair of grooved rods, and are tensioned to form a single sheet of wires extending in a common plane. The single sheet is then sealed without distortion to opposite sides of a frame which were resiliently flexed toward each other prior to the sealing operation and are maintained in their flexed condition during sealing by applied forces which are thereafter relaxed.

The present invention relates to improvements in the manufacture of flat grids used in cathode ray tubes.

It is known that some cathode ray tubes for colour television have a luminescent screen with parallel strips of diflierent phosphors and in front of the screen one or more grids of Wires arranged parallel to the strips on the luminescent screen.

Normally, these grids have a large area, for example, about 1500 sq. cm. and may comprise, for example, nearly five hundred wires.

The slops of the wires, their parallelism and the planarity of the grid must be of a high degree of precision within a limit of one hundredth of a millimetre, for example. The wire tension must be high in order to maintain this precision and, in particular, to avoid vibrational phenomena. The minimum tension of each wire must be 500 grammes and this, in view of their number requires a frame which can support several hundred kilograms.

The method according to the invention is of the general type wherein a sheet of wires corresponding-except for the length of the wiresto that which is to be fixed to the grid frame, is first formed between two parallel grooved rods, hereinafter referred to as positioning rods. The wires are then fixed to the frame, without deformation of the sheet, by sealing them to the grid frame with a fusible sealing substance, in which they are embedded, and thereafter the useful portion of the sheet is separated from the other portions thereof by cutting the wires.

The advantages of this method are immediately apparent.

The precision is provided during the manufacture by the two positioning rods and their supports, that is, a permanent manufacturing apparatus and not by each individual frame.

Any deformation of the used frame remains without effect on the surface of wires produced in the manufacture since this surface is determined by the two positioning rods and any distortion of the frame is compensated by the embedding material.

Preferably, the two positioning rods are threaded.

- However with this method, difiiculties are encountered for obtaining in a convenient way a sufficient tension of the wires at the time of the sealing.

The present invention avoids this drawback and at the same time provides :a very convenient way of forming the desired sheet.

According to the invention, a continuous wire is wound about two spaced, grooved first or winding rods to form two sheets of Wires which are brought to rest on two grooved second or positioning rods. The wires of the two sheets are then tensioned to form a single sheet of wires extending in a common plane between the positioning rods. Forces are exerted to two opposite sides of a resilient frame to move the sides toward each other into a position remote from the relative position of the sides in the relaxed condition of the frame, and the wires of the single sheet are sealed to the opposite frame sides while they are maintained in the afore-mentioned common plane, and while the sides are maintained in their position remote from the relaxed position thereafter After the sealing, the forces exerted on the opposite frame sides are relaxed.

As more specifically applied to a four-sided frame in which the ends of the two afore-mentioned opposite sides are connected by two other sides of the frame, forces are exerted in the method of the invention to respective portions of the opposite sides intermediate the ends thereof for flexing the intermediate portions toward each other prior to the sealing of the same to the wires, and for maintaining the opposite sides in the flexed condition during the sealing.

Conveniently, theintermediate portions of the opposite sides are formed with respective aligned apertures and are flexed by inserting a stay rod. through the apertures so that a threaded end of the stay rod projects from each intermediate portion in a direction away from the other intermediate portion, and by threadedly moving a nut on each end toward the associated intermediate portion to flex the same.

For a better understanding of the invention and to show how the same may be carried into effect reference will be made to the drawing accompanying the following description and in which:

FIG. 1 shows the winding of a double sheet of wires about a Winding support with threaded rods;

FIG. 2 shows the rectangular frame of a grid predistorted by a stay arranged along the smaller axis of the frame parallel to the direction of the wires;

FIG. 3 shows a frame for positioning and tensioning the wires at the level of the grid frame;

FIG. 4 and FIG. 4A respectively are a side elevation and a plan view of the assembly formed by combining the winding support and the wire positioning and tensioning frame;

FIG. 5 shows the method of fixing the ends of the wire to the grid frame assuring full planarity of the sheet of wires in spite of any possible deformation of the grid frame; and

FIG. 6 shows in detail the attachment of one wire end to the grid frame and indicates in cross-section the fusible metal or enamel, and in the latter case the metallizing layer, for rendering the wires equipotential.

The invention will be described with reference to a rectangular grid frame with equidistant parallel wires,

perpendicular to two sides of the grid frame, this corresponding to a very general but not limitative case.

The manufacture of such a plane grid comprises four operations. The first operation will be described with reference to FIG. 1.

A rectangular winding support consists of two channel members 1 connected to two threaded rods 2, the pitch of which is double the distance between the wires in the grid to be made, the whole arrangement being rotatable about a shaft 4. The wire 7 coming from a spool 8 is laid into the threads. The winding is preferably effected by rotating the support about the axis of the shaft 4.

At the start, the wire is fixed by a screw 3 to the left end of the .upper threaded rod and at the end of the operation, by another screw not shown in the drawing, to the right end of the lower threaded rod. Each channel member 1 has holes 5 for fixing it by means of bolts to the wire positioning and tensioning frame, shown in FIG. 3.

The second operation relates to the predeformation of the grid frame, as shown in FIG. 2.

This frame is preferably formed by a metal channel, the open side of which is facing inwardly, as shown at 9 in FIG. 3.

The frame 9 may consist, for example, of a single channel member with a single welded joint or of several channel elements with a suitable number of welded joints.

Prior to the use of the frame and up to the end of the fourth operation the longer sides of the frame, namely, the sides to which the wires will be perpendicular, are bent; this is shown in an exaggerated manner in FIG. 2. This is effected by means of a stay 10 stressed in traction by locking nuts 11.

This preliminary tension has the object of moving the long sides of the grid frame to the deformation limit and thus, to the limit of elasticity, so that the forces applied later to the sides through the tensioning of the wires become negligible compared with the preliminary tensioning of the frame.

This measure has for its object to avoid that, in the ultimately formed sheet of wires, the centre wires would be less taut than the marginal wires.

FIG. 3 shows, in elevation and parallel to the wires of the surface to be formed, the positioning and tensioning frame for the wires which will form the grid.

A rectangular frame, made of channels, of which only one channel 12 is shown, with two sides parallel to the wires of the sheet to be formed supports two cradles 13, and two further cradles not shown are arranged symmetrically to the former relative to the vertical centre plane of the frame, parallel to the wires of the grid to be formed and referred to hereinafter as plane P.

Each cradle has two bearings, of which that nearer the outside of the frame is larger than the other.

The mounting has four supports 16 provided with threaded bores, arranged inside the channel of the frame and permitting the adjustment in height of the grid frame 9 of FIG. 2 by means of four screws screwed into these four supports. The drawing shows a single as sembly 15 16, a portion of channel 12 having been broken away to this effect. Only the point of the corresponding screw of another similar assembly is seen in FIG. 3, this assembly being located symmetrically to the former relative to the centre plane of the frame, perpendicular to the wires of the grid. The trace of this plane is shown in the drawing by a dash-dot line.

Two other assemblies 15-16, are arranged symmetrically to the former relative to plane P.

In the smaller lodgings of the cradle 13 rest the ends of two threaded positioning rods 14 located perpendicularly relative to the plane P.

The pitch of their thread is equal to that of the wires of the grid to be formed.

The four screws 15 are so adjusted that the frame 9 is horizontal.

The third operation consists in positioning and tensioning the grid wires of the winding support of FIG. 1 at the level of the grid frame 9 located on the support of FIG. 3.

This operation is indicated in FIG. 4 which shows how the positioning and tensioning frame 12 is assembled with the winding support 1 by means of bolts 17 inserted into the orifices 5 of the winding support of FIG. 1.

In addition to the elements already mentioned there are two smooth tensioning rollers 18 journaled in the larger lodgings of the cradles 13, channel-shaped locking beams 19 and supporting studs 22. The operation consists, after assembling the positioning and tensioning frame and the winding support together by means of bolts 17, in placing manually the double sheet of Wires, wound around the threaded rods 2, into the threads of the positioning rods 14 in such a way that the wires of the lower sheet rest, for example, at the bottom of the even threads and those of the upper surface, in the odd threads, when the smooth tensioning rollers 18 are lowered by screwing down the studs 22 fixed tothe locking beams 19. Lodgings 13 are narrower at their lower end portion, so that the ends of the rollers 18 cannot reach their bottom. Each end portion of the rollers has a groove which is engaged by the point of the corresponding screw.

This results in a single surface of substantially parallel and uniformly tensioned wires 6 above the frame of the grid 9.

By screwing the screws 15 the grid frame 9 can be raised so that its upper surface substantially reaches the plane of the wires but without allowing the contactof the grid frame to displace the wires of the sheet.

When the frame of the grid 9 is fully even all wires of the surface are positioned at the same distance. If the frame of the grid 9 is slightly distorted certain wires are nearer and others are farther away, but this presents no drawback.

FIG. 4A shows in plan view the same elements, representing only one half of the frame, the two halves being symmetrical relative to plane P.

The wires of the double sheet maintained by the threadt ed rods 2 are positioned in the groove of rods 14 and tensioned by the smooth rollers 18. The holes 20 and screws 21 permit the fixation'of the locking beams 19, carrying studs 22 which serve to tension the wires to the desired extent. The predeformation stay 10 for the grid frame is also shown.

The fourth operation has the object of fixing the wires of the surface 6 to the edges of the longer sides of the grid frame 9. This is achieved by embedding the wires in a sealing material, for example, a metal or an enamel. This additional substance is shown at 23 in FIG. 4, 'FIG. 4A, and FIG. 5.

The latter is a cross-section along a longer side of the grid frame 9 and shows that a surface of wires 6 can maintain its planarity in spite of a mechanical distortion of the grid frame due to the fact that the wires are then embedded at different heights in the retaining layer.

The embedding of the wires, may be effected by conventional means but in order to avoid any drawbacks caused by local heating a preferred method consists in depositing the component substances of the embedding layer 23 at the required points and producing their fusion by introducing the assembly of FIG. 4 into a furnace. After cooling, the stay 10 is removed.

If the embedding layer is not conducting, as in the case of a melting enamel, the electrical connection of the sheet can be obtained by metallizing 24 covering the embedding substance at the ends of the sheet, as shown in FIG. 6, which is a cross-section along the narrow sides of the grid 9.

The choice of materials used for. the frame, the grid wires and the fittings is important.

The coefficient of expansion of the wire metal should be higher than that of the grid frame so that the final tension of the wires is suitable.

The coefficient of expansion of the grid frame, the positioning and tensioning frame and the winding support should be equal, so as to obtain under cold conditions a suitable spacing of the wires.

The invention can be applied to most flat grids, provided adequate winding and positioning rods are used.

In particular, it can be applied to grids with parallel oblique wires, making for example an angle of 45 with the sides of a rectangular frame, in which case all the four sides of the frame will support wires. In that case, the grid frame is laid on the positioning and tensioning frame in its desired position relative to the sheet of wires.

What is claimed is:

1. A. method of making a wire grid for a cathode ray tube which comprises:

(a) winding a continuous wire about two first spaced,

grooved rods to form two sheets of wires;

(b) bringing the two sheets to rest on two second spaced grooved rods;

(c) tensioning the wires of said sheets to form between said second rods a single sheet of wires extending in a common plane;

((1) exerting forces on two opposite sides of a resilient frame to move said sides toward each other into a position remote from the relative position of said sides in the relaxed condition of said frame;

(e) sealing the wires of said single sheet to said opposite sides while maintaining said wires in said common plane and while maintaining said sides in said remote position thereof; and

(f) thereafter relaxing said forces.

2. A method as set forth in claim 1, wherein said frame has four sides, the ends of said two opposite sides being connected by two other sides of said frame, and

said forces are exerted on respective portions of said opposite sides intermediate the ends thereof for flexing said intermediate portions toward each other prior to said sealing, and for maintaining said opposite sides in the flexed condition during said sealing.

3. A method as set forth in claim 2, wherein said intermediate portions are formed with respective aligned apertures, and said intermediate portions are flexed by inserting a stay rod through said apertures so that an end of the stay rod projects from each of said intermediate portions in a direction away from the other intermediate portion, said end being threaded, and threadedly moving a nut on each end toward the associated intermediate portion to flex the same.

References Cited UNITED STATES PATENTS 2,068,675 1/1937 Heller -92.2 2,772,376 11/1956 Cook et a1. 14071.5 2,824,251 2/1958 Patterson 14071.5 2,998,033 8/1961 Sandor 14071.5 3,212,532 10/1965 Szilasi et al. 140-715 RICHARD J. HERBST, Primary Examiner. L. A. LARSON, Assistant Examiner. 

1. A METHOD OF MAKING A WIRE GRID FOR A CATHODE RAY TUBE WHICH COMPRISES: (A) WINDING A CONTINUOUS WIRE ABOUT TWO FIRST SPACED, GROOVED RODS TO FORM TWO SHEETS OF WIRES; (B) BRINGING THE TWO SHEETS TO REST ON TWO SECOND SPACED GROOVED RODS; (C) TENSIONING THE WIRES OF SAID SHEETS TO FORM BETWEEN SAID SECOND RODS A SINGLE SHEET OF WIRES EXTENDING IN A COMMON PLANE; (D) EXERTING FORCES ON TWO OPPOSITE SIDES OF RESILIENT FRAME TO MOVE SAID SIDES TOWARD EACH OTHER INTO A POSITION REMOTE FROM THE RELATIVE POSITION OF SAID SIDES IN THE RELAXED CONDITION OF SAID FRAME; (E) SEALING THE WIRES OF SAID SINGLE SHEET TO SAID OPPOSITE SIDES WHILE MAINTAINING SAID WIRES IN SAID COMMON PLANE AND WHILE MAINTAINING SAID SIDES IN SAID REMOTE POSITION THEREOF; AND (F) THEREAFTER RELAXING SAID FORCES. 